1. Field of the Invention
The present invention relates generally to solar cells, and more particularly but not exclusively to solar cell fabrication processes and structures.
2. Description of the Background Art
Solar cells are well known devices for converting solar radiation to electrical energy. They may be fabricated on a semiconductor wafer using semiconductor processing technology. Generally speaking, a solar cell may be fabricated by forming P-type and N-type diffusion regions in a silicon substrate. Solar radiation impinging on the solar cell creates electrons and holes that migrate to the diffusion regions, thereby creating voltage differentials between the diffusion regions. In a backside junction solar cell, both the diffusion regions and the metal contact fingers coupled to them are on the backside of the solar cell. The contact fingers allow an external electrical circuit to be coupled to and be powered by the solar cell.
For cost reasons, inkjet printing steps have been developed for use in back end processes involving electrical connection of a metal contact finger to a corresponding diffusion region. More specifically, a contact mask defining a contact hole through which a metal contact finger may be electrically connected to a diffusion region may be formed by inkjet printing. However, the contact mask typically requires critical alignment with other features of the solar cell wafer. This alignment limits the processing parameters of other steps in the back end process.